Rotation control sensor

ABSTRACT

A rotation-monitoring detector including a binary output signal and a signaling LED, and including a frequency operating mode in which the state of the output signal and of the LED are a function of a passage frequency of a target in front of the detector. The detector also includes a static operating mode in which the state of the LED is a function of a distance between the target and the detector. The detector also includes a selector, permitting the static operating mode and the frequency mode to be selected. The selector is also used for learning functions of the detector.

The present invention relates to a proximity detector of the inductive,capacitive, magnetic, or photoelectric type, or to a mechanical positionswitch used for monitoring rotation, particularly in the monitoring ofunder-speed or over-speed of a rotational movement.

Rotation control detectors are frequently used in numerous industriesfor monitoring movement, slipping, conveyor belt breaks, belt breaks,etc. They unite, in the same device, conventional functions of detectingthe presence of a target close to, or in contact with, the detector bymeans of a sensor element and functions of processing by counting theinformation received by the detector during a given time for comparisonwith, for example, a predetermined frequency of engagement of the deviceso as to deliver as an output a binary signal resulting from thiscomparison. An economical device is thus obtained, well suited todealing with simple problems of under-speed and over-speed.

The document EP 1130403 describes a rotation-monitoring detector, infront of which there passes a target whose frequency of passage is to bemonitored with respect to a normal passage frequency. This detectorcomprises operator communication means constituted by a push button andan electroluminescent communication diode LED on the detector. The pushbutton acts to place the detector in a working mode or in a learningmode. The learning mode permits the microcontroller of the detector tomeasure a normal passage frequency and permits selecting a range ofdetector functioning around this normal frequency. In the learning mode,the communication LED associated with the push button acts, for example,to guide the operator in the adjustment of the desired range of detectorfunctioning. Furthermore, such a detector also generally comprises adisplay LED which is the image of the state of the output.

However, during the mounting of a rotation-monitoring detector, it ishardly practical to adjust the distance of the target in static mode soas to situate it in the range of the detector. For this, it would bequite effective to give the assembly operator, during the initialadjustment phase, information indicating to him whether or not thetarget is placed at a satisfactory distance within the range of thedetector. There exist certain rotation-monitoring detectors which havefor this purpose, as well as an LED to display an image of the frequencyof passage of the target, another specific display LED whose state is afunction of the distance between the target and the detector. However,this solution is expensive, because it requires a supplementary displaycomponent which is only used in the initial adjustment phase and whichcan furthermore result in excessive electric consumption in a small sizedevice, particularly in a two-wire supply version.

The present invention has as its object to remedy these disadvantages byproposing an economical solution which gives the operator informationindicating to him, during the adjustment phase of the detector, whetherthe target is or is not situated in the range of the detector.

For this, the invention describes a rotation-monitoring detectordelivering a binary output signal and having a signaling LED, the stateof the binary output signal and of the signaling LED being a function,in a frequency operating mode, of the passage frequency of a target infront of the detector. The detector is characterized in that it has astatic operating mode in which the state of the signaling LED is afunction of the distance D between the target and the detector.

According to a characteristic, the state of the output signal, in thestatic mode, is a function of the distance D between the target and thedetector.

According to another characteristic, the detector comprises selectionmeans positioned in a first position or in a second position, permittingthe selection of the static mode and the frequency mode. The selectionmeans are likewise used for parameterizing the learning of the detectorin frequency mode. Preferably, the selection means are constituted by apush button, the pressed state of which corresponds to the secondposition.

Other characteristics and advantages will become apparent from thefollowing detailed description, referring to an exemplary embodimentrepresented by the accompanying drawings in which:

FIG. 1 shows a schematic view of a detector according to the invention,

FIG. 2 shows the different modes of functioning of the detector.

Referring to FIG. 1, a detection device 10 is responsible for monitoringthe frequency of passage of one or more targets 20 so as to detect anunder-speed and/or an over-speed with respect to a normal passagefrequency.

The detection device 10, termed “detector” in the present document, mayequally be either an inductive, capacitive or magnetic proximitydetector or a photoelectric cell monitoring the passage of a targetsituated at a distance D from the detector, or else a mechanicalposition switch monitoring the passage of a target situated in contactwith the detector. The embodiment described hereinbelow corresponds to aproximity detector.

It is known that such a detector 10 comprises a sensor element,sensitive to the passage of the target 20 and constituting theinformation input of the detector 10. The sensor element emits a sensorsignal, the state of which is a function of the distance of the target20. This sensor signal is transmitted, via an amplifying and shapingstage, to a processing unit which processes it so as to deliver, througha power stage, a binary output signal 15 which can be either in thestate 0 or in the state 1. In a use of the detector 10 as a rotationmonitor, the binary output signal 15 is thus a function of the frequencyof passage of the target in front of the detector, in frequencyoperating mode. For example, it may be envisaged that the output signal15 is in state 1 when the passage frequency of the target 20 is greaterthan a given engagement frequency, and in state 0 if not, taking accountof hysteresis. It can likewise be envisaged that the output signal 15 isin state 1 (or respectively state 0) when the passage frequency of thetarget 20 is comprised within an operating range around a given nominalpassage frequency, and in state 0 (or respectively state 1) outside thisrange. The detector 10 also comprises a signaling LED 16, for exampleyellow in color, which is traditionally the image of the output 15.

Furthermore, the detector 10 for rotation monitoring comprises operatorcommunication means 11 connected to the microcontroller and comprising acommunication LED 12, for example green in color, as well as selectionmeans 13 positioned in a first position or in a second position. Thecommunication LED 12 is moreover frequently used to indicate thedetector power supply.

The rotation-monitoring detector works according to a frequencyoperating mode 30 which includes two operating sub-modes: a working mode31 and a learning mode 32. The working mode 31 corresponds to the usualoperation of the detector 10 in which this monitors the passage of atarget 20 and delivers a binary signal 15 which is a function of thepassage frequency of this target 20. In the working mode 31, thesignaling LED 16 is directly the image of the binary output 15, forexample lit when the binary output 15 is in state 1. It may thus aid anoperator close to the detector to verify the good operation of thedetector.

The learning mode 32 permits performing the parameterization of thedetector 10. This learning mode comprises the following phases, forexample:

-   -   measurement of a normal passage frequency, starting from a        target passing in front of the detector at a reference speed,    -   calculation of an engagement frequency and of a disengagement        frequency from the normal measured passage frequency and from an        operating range chosen by the operator.

To actuate the learning mode 32, then to parameterize the detector 10 inthis learning mode 32 in order in particular to select the desired rangeof operation, the operator uses the selection means 13 and thecommunication LED 12, following an appropriate communication protocol,such as that described in the document EP 1130403.

Nevertheless, before performing learning of the detector 10, a firstoperation is necessary to ensure good positioning of the target 20, thatis, to ensure that the distance D between the target 20 and the detector10 is comprised in the range of the detector 10 when the target 20passes in front of the detector 10. This adjustment operation isexecuted during the initial assembly of the detector, during positioningof a target 20, but also during periodic maintenance operations, etc.

If it is performed with the passage of a target 20 in rotation, theadjustment operation may become extremely dangerous because of thepresence of moving parts close to the operator. It is thus highlydesirable to execute this adjustment before any operation of the machineon which the detector 10 is fixed. But if the adjustment operation isperformed at very low speed or at zero speed to avoid this danger, theintegration time necessary for the detector 10 for calculating a speedand sending a corresponding signal is necessarily very long, which makesthe adjustment of the range tedious. Furthermore, during this adjustmentoperation, the operator needs to have a rapid return of informationindicating to him whether the target 20 is at a correct distance fromthe detector 10.

For this reason, the invention describes a detector 10 for rotationmonitoring having the possibility of performing this adjustment by meansof a supplementary operating mode called “static mode” 35. In thisstatic mode 35, the state of the signaling LED 16 is no longer afunction of the passage frequency of the target 20 past this, as in theworking mode 31, but is uniquely a function of the position of thetarget 20 with respect to the detector 10, that is, the distance Dbetween the target 20 and the detector 10. For example, the LED 16 islit only if the distance D between the target 20 and the detector 10 iswithin the range of the detector 10. Thus an operator performing theadjustment of the detector 10 may directly visualize an item ofinformation indicating to him whether the detector 10 (or the target 20)is correctly positioned, permitting the adjustment of the distance D tobe very rapidly carried out.

In the static mode 35, the binary output 15 is generally a function ofthe distance D between the target 20 and the detector 10, thus behavinglike the display LED 16, but can likewise remain a function of thepassage frequency of the target 20, as in the frequency mode 30. In thefirst case, the static mode 35 is then similar to the operating mode ofa conventional proximity detector not operating as a rotation monitor.

Advantageously, by manually or automatically varying the position of thetarget, the static mode 35 also permits verifying at any time, at theend of manufacture but also on site, that the detector 10 indeed has ahysteresis in the detection of range. This hysteresis is controlled bythe builder and is necessary to minimize any risk of the sensor elementrebounding at the moment of the rising or falling fronts of the targetpresence sensor signal. It is vital to verify this hysteresis because,when used as a rotation monitor, such a rebound would inevitablyintroduce an error into the counting and would thus generate apotentially erroneous output signal 15 of the detector 10.

As the static mode 35 and the learning mode 32 are never simultaneous,as indicated in FIG. 2, then according to the invention the operatorcommunication means 11 used during the learning mode 32 is likewise usedto select the static mode 35 or the frequency mode 30 without penalizingthe functionalities of the detector 10. It is thus very economical topropose a static adjustment mode 35 such as described hereinabove in therotation-monitoring detectors 10 already having a learning mode 32,since no addition of supplementary components is necessary. Aconsiderable supplementary service for the operator is thus easilyprovided to aid him in setting up his installation.

In particular, the selection means 13 permit selecting the static mode35 in the following manner:

-   -   if the selection means 13 of the detector 10 are positioned in        the first position at the switching on of the detector 10 (that        is the moment of applying voltage to the detector 10), the        frequency mode 30 (including the working mode 31 and the        learning mode 32) is selected,    -   if the selection means 13 of the detector 10 are positioned in        the second position at the switching on of the detector 10, the        static mode 35 is selected.

According to a first embodiment, the selection means are constituted bya simple push button 13 placed close to the communication LED 12, thuspreserving a simple solution for the detector 10. The first position ofthe selection means corresponds to the relaxed, or non-active, state ofthe push button 13, and the second position corresponds to the pressed,or active, state of the push button 13.

In this embodiment, passing from the frequency mode 30 to the staticmode 35 requires shutting off the power supply to the detector 10, thenpressing the push button 13 and restoring the power supply to thedetector 10. Vice versa, passing from the static mode 35 to thefrequency mode 30 requires shutting off the power supply to the detector10, then restoring the power supply to the detector 10 without pressingthe push button 13. Once one of the static mode 35 or frequency mode 30has been selected, the push button 13 has no influence on returning tothe frequency 30 or static 35 mode, as long as the power supply to thedetector 10 is not shut off. Because of the use of a push button,shutting off the power supply of the detector 10 during normal operationautomatically places the detector by default in the frequency mode 30corresponding to normal operation, since the push button 13 is bydefault in its relaxed position.

According to another embodiment, the selection means 13 are constitutedby a two-position bistable switch. In this case, a proximity detector isobtained which has two distinct operating modes which are equallyusable: if the switch is in a first position when voltage is applied,the detector operates in frequency mode as a rotation monitor with anoutput whose state is a function of the passage frequency of a target;if the switch is in a second position when voltage is applied, thedetector operates in static mode as a conventional proximity detectorwith an output whose state is a function of the position of a target.

It is of course possible to imagine, without departing from the scope ofthe invention, other alternatives and improvements of detail, and toenvisage the use of equivalent means.

1-8. (Canceled).
 9. A rotation-monitoring detector comprising: a binary output signal; a signaling LED; a frequency operating mode in which a state of the binary output signal and a state of the signaling LED are a function of a passage frequency of a target in front of the detector; and a static operating mode in which the state of the signaling LED is a function of a distance between the target and the detector.
 10. A rotation-monitoring detector according to claim 9, wherein in the static operating mode, the state of the output signal is a function of the distance between the target and the detector.
 11. A rotation-monitoring detector according to claim 9, wherein in the static operating mode the signaling LED is lit when the distance of the target is within a range of the detector.
 12. A rotation-monitoring detector according to claim 10, further comprising means for selecting positioned in a first position or in a second position, for permitting selection of the static operating mode and of the frequency operating mode.
 13. A rotation-monitoring detector according to claim 11, further comprising means for selecting positioned in a first position or in a second position, for permitting selection of the static operating mode and of the frequency operating mode.
 14. A rotation-monitoring detector according to claim 12, wherein the means for selecting is also used for parameterizing learning of the detector in the frequency operating mode.
 15. A rotation-monitoring detector according to claim 13, wherein the means for selecting is also used for parameterizing learning of the detector in the frequency operating mode.
 16. A rotation-monitoring detector according to claim 14, wherein the means for selecting includes a push button whose pressed state corresponds to a second position.
 17. A rotation-monitoring detector according to claim 15, wherein the means for selecting includes a push button whose pressed state corresponds to a second position.
 18. A rotation-monitoring detector according to claim 12, wherein the frequency operating mode is selected when the means for selecting is positioned in a first position during switching on of the detector.
 19. A rotation-monitoring detector according to claim 15, wherein the frequency operating mode is selected when the means for selecting is positioned in a first position during switching on of the detector.
 20. A rotation-monitoring detector according to claim 18, wherein the static operating mode is selected when the means for selecting is positioned in a second position during the switching on of the detector.
 21. A rotation-monitoring detector according to claim 19, wherein the static operating mode is selected when the means for selecting is positioned in a second position during the switching on of the detector. 